Pope Francis delivers first Christmas Eve homily: 'Do not be afraid!'

Pope Francis kisses a statue of baby Jesus as he celebrates the Christmas Eve Mass in St. Peter's Basilica at the Vatican, on Dec. 24.

By Elisha Fieldstadt, NBC News

The faithful flocked to St. Peter's Basilica for Pope Francis' first Christmas Eve midnight Mass, in which the pontiff once again preached the importance of acceptance and humility, qualities he has demonstrated continually in his first nine months as head of the Catholic Church.

"The people who walked in darkness have seen a great light," Francis began, quoting from Isaiah, a book of the Bible that includes prophesies foretelling the birth of Jesus.

Pope Francis offered a traditional lesson of light and love during his first Christmas Eve midnight Mass in St. Peter's Basilica in the Vatican. NBC's Martin Fletcher reports.

Jesus brought light and grace to the world, and that grace "made salvation possible for the whole human race," Francis said, choosing to highlight a scripture from the biblical book of Titus.

While Jesus embodied light and love, Francis said, those who hate walk in "darkness."

"If we love God and our brothers and sisters, we walk in the light; but if our heart is closed, if we are dominated by pride, deceit, self-seeking, then darkness falls within us and around us," the pontiff said.

Francis, who celebrated the Mass with more than 300 cardinals, bishops and priests, urged people not to be afraid to reach out to God - echoing the words of the biblical angel delivering news of Jesus' birth.

"Do not be afraid! Our Father is patient, he loves us, he gives us Jesus to guide us on the way which leads to the promised land. Jesus is the light who brightens the darkness. He is our peace," he said.

Francis has sought to change the image of the Catholic Church as a judgmental, lavish, inflexible institution since his election in March.

Of gay priests, he has asked, "who am I to judge?" He has washed the feet of prisoners, refused to move into the papal palace and celebrated his recent birthday breakfast with three homeless men. On Monday, he made a Christmas visit to Pope Emeritus Benedict and asked him to pray for him.

"(He) is bringing a new era into the Church, a Church that is focusing much more on the poor and that is more austere, more lively, a Church that cares about everyone in the world," said Dolores Di Benedetto, who traveled from the pope's homeland, Argentina to hear him speak.

“I thought it would be very nice to hear the words of this pope close up and to see how the people are overwhelmed by him," said Giacchino Sabello, one of more than 10,000 people who packed St. Peter's Basilica or stood outside watching the ceremony on mega-screens.

In Christmas Eve's Mass, Francis reiterated the importance of reaching out to the downtrodden, using the shepherds who were the first to hear of Jesus' birth as an example. "They were the first because they were among the last, the outcast," he said.

"We bless you, Lord God most high, who lowered yourself for our sake. You are immense, and you made yourself small; you are rich and you made yourself poor; you are all-powerful and you made yourself vulnerable," said Francis in thanks to God and also a clear indication of the humility he encourages his flock to emulate.

Ettore Ferrari / EPA

Pope Francis leads the midnight Christmas Mass in St. Peter's Basilica at the Vatican late on Dec. 24.

In his address to Vatican administrators on Saturday, Francis said holiness was a practice of "deep humility and fraternal charity in our relationships with our fellow workers," as he urged the cardinals, bishops and priests to avoid gossip.

Before the Mass, Francis further inspired meekness, when he personally placed a baby Jesus doll in a replica of a manger, a custom usually performed by an aid.

The 2 1/2-hour Mass was the first of many services Francis will lead during the holidays. On Christmas Day, he will deliver a "Urbi et Orbi" (to the city and the world) message from the basilica's balcony overlooking St. Peter's Square.

He will also hold mass on New Year’s Eve and New Year’s Day and another on Jan. 6, for the feast of the Epiphany or “Three Kings’ Day,” celebrating the Magi’s visit to the baby Jesus.